Fix Ingress resources in docs (#7579)

* fix Ingress resources in docs

Signed-off-by: Gerald Pape <gerald@giantswarm.io>

* move to ingressClassName

* fix more Ingress resource examples

* empty commit

Signed-off-by: Gerald Pape <gerald@giantswarm.io>

* make NOTES.txt aware of version + add notice about ingress version to examples main page

* add link to legacy documentation

Signed-off-by: Gerald Pape <gerald@giantswarm.io>

charts/ingress-nginx/README.md

@@ -2,13 +2,14 @@
 
 [ingress-nginx](https://github.com/kubernetes/ingress-nginx) Ingress controller for Kubernetes using NGINX as a reverse proxy and load balancer
 
-To use, add the `kubernetes.io/ingress.class: nginx` annotation to your Ingress resources.
+To use, add `ingressClassName: nginx` spec field or the `kubernetes.io/ingress.class: nginx` annotation to your Ingress resources.
 
 This chart bootstraps an ingress-nginx deployment on a [Kubernetes](http://kubernetes.io) cluster using the [Helm](https://helm.sh) package manager.
 
 ## Prerequisites
 
-- Kubernetes v1.16+
+- Chart version 3.x.x: Kubernetes v1.16+
+- Chart version 4.x.x and above: Kubernetes v1.19+
 
 ## Get Repo Info
 
@@ -177,8 +178,8 @@ controller:
         networking.gke.io/load-balancer-type: "Internal"
         # For earlier versions
         # cloud.google.com/load-balancer-type: "Internal"
-        
-        # Any other annotation can be declared here. 
+
+        # Any other annotation can be declared here.
 ```
 
 Example for Azure:

charts/ingress-nginx/templates/NOTES.txt

@@ -29,23 +29,30 @@ Get the application URL by running these commands:
 
 An example Ingress that makes use of the controller:
 
+{{- $isV1 := semverCompare ">=1" .Chart.AppVersion}}
   apiVersion: networking.k8s.io/v1
   kind: Ingress
   metadata:
     name: example
     namespace: foo
+    {{- if eq $isV1 false }}
+    annotations:
+      kubernetes.io/ingress.class: {{ .Values.controller.ingressClass }}
+    {{- end }}
   spec:
-    ingressClassName: example-class
+    {{- if $isV1 }}
+    ingressClassName: {{ .Values.controller.ingressClassResource.name }}
+    {{- end }}
     rules:
       - host: www.example.com
         http:
           paths:
-            - path: /
-              pathType: Prefix
-              backend:
+            - backend:
                 service:
                   name: exampleService
-                  port: 80
+                  port:
+                    number: 80
+              path: /
     # This section is only required if TLS is to be enabled for the Ingress
     tls:
       - hosts: